1P0Z:
reference: The structure of the periplasmic ligand-binding domain of the sensor kinase CitA reveals the first extracellular PAS domain., Reinelt S, Hofmann E, Gerharz T, Bott M, Madden DR, J Biol Chem 2003 Oct 3;278(40):39189-96. Epub 2003 Jul 16. PMID: 12867417

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).